Can a creatures tell if what it is looking at is invisible?

[Camman1984]

If a creature, in this case a Tressym, has the ability to see things that are magically invisible. Can it tell that the creature is trying to be invisible or does it just appear normal? For example, if I tell my tressym to meow if it sees an invisible creature, will it work? (It is intelligence 11 and understands common)

[DevanAvalon]

Yeah, they probably would. They'd see it as "transparent" imo, so enough to know that it is there, and since it's see-through, it's invisible. but that's my interpretation of it all.

[RedMage125]

I'd be inclined to agree.

With one exception. True Seeing. That spell so accurately sees through all illusions that one doesn't even detect the original illusion.

[PhantomSoul]

Usual disclaimer: thoroughly in the DM's court, and there's definitely reason to rule either way for both of those questions.

That aside, as a DM I'd say it highly depends on the source that overcomes, ignores or detects invisibility. (And as a player in the games where I'm not the DM!)

In the case of the Tressym, it's conflicting; the name of the trait


Detect Invisibility

implies that the Tressym might (though it seems odd to say "Detect Invisible" as a 5e Trait, just in terms of style; it's Detect Magic, not Detect Magical, for instance), but the description leads me to think it just ignores invisibility, not that it detects the presence of invisibility:


Within 50 feet of the tressym, magical invisibility fails to conceal anything from the tressym's sight.

How I find it most intuitive and flavourful to picture from only that information is that the Tressym just sees through magical invisibility, and therefore sees invisible things as normal. I've found that can be fun when it's a player's ability because then the player (character) combines information with other player( character)s to get the full picture... but if it's a familiar, that's negated (it just tells the player to sense through their familiar, but that does create a decision because it takes an action every turn), and the question largely becomes how independent a familiar is when playing with that DM. If it's a pet, it becomes a bit more interesting again; it encourages people to interact with the pet more like a character, and reinforces that they're part of the in-game interactions. I like having uncontrolled familiars being treated like pets anyhow, so it works out in my games.

If the Forgotten Realms Wiki is reliable, it says the Tressym can "sense" rather than "see", in which case detecting the presence of magical invisibility seems fitting. That's especially true if they can compare senses (e.g. a bat locating a creature through echolocation [blindsight] while also being able to see that no creature is visible in the echolocated location).

Regardless, I'd probably default not only to the creature being perceptible (through those senses), but to the presence of invisibility being detectable (given the trait name -- but not description -- which is reinforced by the wiki info).

But again, of course, you should ask your DM if you're not the DM. It seems reasonable to rule any witch way for this given the official information.

[kazaryu]

I'd be inclined to agree.

With one exception. True Seeing. That spell so accurately sees through all illusions that one doesn't even detect the original illusion.

I disagree. The way truesoght reads, it implies that you automatically percieve an illusion for what it is. Not that you never see the illusion. Youre just automatically not fooled by it.

[1Pirate]

For example, if I tell my tressym to meow if it sees an invisible creature, will it work?

Not really. Getting a cat to do one thing you say once requires a DC 35 Persuasion check at disadvantage.

[Joe the Rat]

Given the way the tressym ability works, something suddenly appearing within 50' ought to be a giveaway.

But I generally take the abilities - detect invisible, true seeing, etc. to reveal the truth behind the illusion, but also what the illusion is (semi-transparent or greyscaled for invisible, the illusion a faint double-image, etc.) This is the usual take for penetrating illusions through "natural" means - you are still aware it is there, but it no longer impedes your perceptions.

The complete inability to see the obscuring effect is a fun thing to play with. I have a player who's character is completely immune to illusions - she cannot perceive them at all. So she's always confused when the rest of the party keeps trying to find a way around empty space, or completely ignores someone hostile in their midst. She also can't read illusory script. Which has nothing to do with the Eyes of the Runekeeper Invocation at all.

[Camman1984]

Not really. Getting a cat to do one thing you say once requires a DC 35 Persuasion check at disadvantage.

As a cat owner I fully endorse this statement and expect it to look at my in disgust when I tell it it should have been on guard duty instead of licking it own but


Thanks for the comments guys, food for thought. I like the idea if seeing invisibility allowing the observer to still know that the creature is invisible personally.

[Keravath]

I would tend toward the interpretation that you can tell that a creature is invisible. The rules don't say specifically but my preference when running it would be to simply tell the player that they see an invisible creature. It is revealed but something different about it would let the viewer know it is invisible.

From a practical perspective, invisible creatures would be obviously invisible if there is any sort of light source (dim or bright). In any case like this the world is full of shadows. Glance around whatever room you are in, the walls, floor ceiling, the entire environment is covered with a varying gradation of shadow. We just don't usually look at it. An invisible creature will have no shadows. If a creature has practiced viewing invisible creatures then they will stand out in their environment simply because they have no shadows, cast no shadows and do not interact with light in any way.

It's the same reasoning for why a creature with devil's sight can immediately tell that the world is actually dark even though they can see clearly. If the scene was due to natural lighting there would be shadows. However, viewing a scene that is completely dark would have no shadows when viewed with devils sight and this would be VERY obvious. No shadows under chairs, no surface illumination variation, it would look very different from normal vision.

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One interesting side effect of the See Invisible spell:

"For the duration, you see invisible creatures and objects as if they were visible"

How do you read this for creatures in darkness? If you can't see in the dark or through magical darkness, is an invisible creature visible to you anyway? The spell says that you see invisible creatures as if they were visible which can be read to say that invisible creatures become visible whether you could normally see them or not. If that is the case, then see invisibility should be easily able to distinguish whether a creature is invisible or not since there must be a visual effect to make them stand out even in complete darkness.

Does see invisibility defeat Blindness? If you have cast see invisibility can you still see the invisible creature if you are blinded?